Praseodymium is one of only two elements, and the only one stable enough to actually have in an element collection, whose names are so long I couldn't engrave them using the normal font size I used for all the other elements. (The other one is rutherfordium an element that exists only for brief periods of time in a few research laboratories, and that only when they happen to be interested in making some. Quite a few other elements required that I manually cramp the inter-letter spacing, but only two were so hopeless I had to use smaller letters.)

All the rare earths are rather similar to each other, and praseodymium is no exception.

Cube under oil.
This is a substantial cube of a relatively reactive rare earth (hence the "under oil" part).

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.

Lump.
This sample arrived with a full set of lanthanides at a time when I was missing europium, terbium, holmium, ytterbium, and of course lutetium.

This very kind donation from Max Whitby of The Red Green & Blue Company in England completed my element collection, to the extent that it gave me a plausible sample of every element one can plausibly have a sample of. (The Red Green & Blue Company is selling a periodic table collection containing similar samples of the same stuff, and if you want a ready-made collection of elements, that's the first place I would look.)

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Hollow cathode lamp.
Lamps like this are available for a very wide range of elements: Click the Sample Group link below to get a list of all the elements I have lamps like this for. They are used as light sources for atomic absorption spectrometers, which detect the presence of elements by seeing whether a sample absorbs the very specific wavelengths of light associated with the electronic transitions of the given element. The lamp uses an electric arc to stimulate the element it contains to emit its characteristic wavelengths of light: The same electronic transitions are responsible for emission and absorption, so the wavelengths are the same.
In theory, each different lamp should produce a different color of light characteristic of its element. Unfortunately, the lamps all use neon as a carrier gas: You generally have to have such a carrier gas present to maintain the electric arc. Neon emits a number of very strong orange-red lines that overwhelm the color of the specific element. In a spectrometer this is no problem because you just use a prism or diffraction grating to separate the light into a spectrum, then block out the neon lines. But it does mean that they all look pretty much the same color to the naked eye.
I've listed the price of all the lamps as $20, but that's really just a rough average: I paid varying amounts at various eBay auctions for these lamps, which list for a lot more from an instrument supplier.
(Truth in photography: These lamps all look alike. I have just duplicated a photo of one of them to use for all of them, because they really do look exactly the same regardless of what element is inside. The ones listed are all ones I actually have in the collection.)Source:eBay seller heruurContributor:Theodore GrayAcquired:24 December, 2003Price: $20Size: 8"Purity: 99.9%Sample Group:Atomic Emission Lamps

Advertising set.
This lovely little set of rare earth oxides was made to promote the fact that rare earths really aren't very rare. Once the technology was developed to separate and purify then economically, they became quite common in fact. There is no date on this piece which is a pity, but I would guess it was made in the 1960's.Source:SoCal (Nevada), IncContributor:Theodore GrayAcquired:23 July, 2004Price: $20Size: 8"Purity: >20%

Fake peridot.
Peridot is a valuable type of gemstone. This is cheap cubic zirconia colored to look like peridot, in much the same way that uncolored cubic zirconia simulates diamond. What makes it interesting to me is that praseodymium is used to impart just the right fake shade of yellow to cubic zirconia to make it look like peridot. There are not a whole lot of other things you can do with praseodymium, so I'll take it!Source:Pehnec GemsContributor:Theodore GrayAcquired:24 March, 2009Text Updated:24 March, 2009Price: $1Size: 0.3"Purity: 1%

Praseodymium-core carbon rods.
Rods like this (about 1/2" diameter) are used, or at least used to be, in the motion picture industry to create large amounts of light for filming. They contain a core (visible in this photo) of a mixture of rare earths which, when vaporized in the arc, provide a daylight spectrum of light. This use is very similar to the way the rare earths provide daylight spectrum light in modern sealed arc lights, just out in the open air.Source:eBay seller saturngroupContributor:Theodore GrayAcquired:16 April, 2009Text Updated:17 April, 2009Price: $22/boxSize: 12"Purity: <20%

Didymium glasses.
This is a lens from a pair of didymium eye glasses meant for glassblowers. The "di" refers to "two", the "dymium" refers to the two elements in the glass, which both end in "dymium". Those two are praseodymium and neodymium. Together they cause the glass to strongly absorb the sodium yellow emission line that creates the bring glow when glass is molten. Wearing them you can stare directly into the molten glass and see only a dull glow from the torch.Source: eBayContributor:Theodore GrayAcquired:24 March, 2009Text Updated:25 March, 2009Price: $50Size: 2"Composition:PrNd

Insane mineral capsules.
These minerals capsules are called "Immune Boost 77", from Morningstar Minerals. They are either being incredibly honest, or they really don't understand what they're saying when they list what amounts to nearly the entire periodic table on the label, as the "trace minerals" they contain.

Some of them are just silly, like thulium, which has absolutely no biological function. Others are a bit scarier, like thallium and thorium that are deadly poisons, and tellurium, which makes you smell of rotten onions for weeks.

Basically what they've done is list everything that occurs in even trace amounts in mixed monazite sand, which is kind of what the stuff inside looks like. The only reason they aren't seriously harmful (I assume) is that most of these are not actually present in any meaningful quantity.

My attention is drawn to these and other similar mineral supplements every time I decide to see if anything interesting has popped up on eBay for one or another of the obscure rare earths. Generally speaking if you search eBay for those guys you get very little of interest unless you turn on the option to search the text of the item description as well as the titles. Then you get lots of trace mineral supplements that one can only hope don't actually contain them.

Himalayan sea salt.
There is a list of 84 elements that seems to pop up repeatedly in the ingredient lists of "natural" mineral products, supplements, pills, and the like. Even, it turns out, in salt. Here then is the list of minerals claimed to be found in all-natural organic Himalayan sea salt:

I wish someone would tell these people that, for example, neptunium and plutonium do not occur in nature at all, let alone in salt. Unless, I suppose, if you count nuclear fallout as a "natural" source of ingredients.
What bothers me most is what this says about the level of scientific literacy, both of the people selling the stuff, and the people buying it. Does no one actually read the list? Or do they read it an not realize how preposterous it is? It's enough to make you despair for the future of mankind.
Pretty salt, though.Source:eBay seller saltwondersContributor:Theodore GrayAcquired:28 March, 2009Text Updated:4 April, 2009Price: $15Size: 0.25"Composition:NaClSbCsDyErEuGdHfHoInLaLuNdPrSmScThTlTeTbTmYbY